The present invention relates to a golf ball having a core and a cover of one or more layer which has been molded over the core. More specifically, the invention relates to a golf ball having an outstanding paint film adhesion and a good durability.
Golf ball covers that use conventional thermoplastic polyurethane materials have a poor mold releasability when molded. To address this problem, use has been made of metal salts of stearic acid or polyethylene waxes as lubricant ingredients or dispersants. However, although an advantage of metal salts of stearic acid is that they increase mold releasability, perhaps because metal salts act as decomposition catalysts for thermoplastic polyurethane materials, it has been confirmed that when a metal salt of stearic acid is used as a dispersant, the metal salt lowers the heat resistance of the thermoplastic polyurethane material. As for polyethylene waxes, owing to their poor compatibility with thermoplastic polyurethane materials, when a polyethylene wax is used as a dispersant, the pigment dispersibility tends to worsen.
To provide a thermoplastic polyurethane material having an excellent mold releasability, JP-A 2002-336382 discloses a cover material which is composed primarily of a thermoplastic polyurethane material and includes also a fatty acid amide and/or montan wax.
In addition, JP-A 2001-348467 describes art which uses both a fatty acid amide and montan wax together in a resin composition for golf balls so as to give the composition a good heat resistance, flow properties and moldability, and obtain high-performance golf balls having an excellent rebound. Moreover, JP-A 2011-31020 describes the use of, as lubricants which are compounded with a base polymer for an outermost cover layer, both (A) a fatty acid amide, and (B) a composition based on a fatty acid which has 24 to 34 carbons and is selected from the group consisting of esters of montanic acid, partially saponified esters of montanic acid and metal salts of montanic acid.
In the above-cited art, the cover material contains a base resin such as a urethane resin in which both a montan wax and an amide wax are used. However, in golf balls which use such a cover material, when paint is applied to the surface of the ball, raising the temperature setting of the mold may cause the wax ingredients to bleed out to the surface and form a film, which may lead to undesirable effects such as peeling of the paint film.